In his veto letter sent to the Legislature, Snyder said the bill had a fatal loophole that didn't allow for those institutions to opt out of the new legislation and prohibit weapons from their buildings.

"I believe that it is important that these public institutions have clear legal authority to ban weapons from their premises," he said in his letter. "Each is entrusted with the care of a vulnerable population and should have the authority to determine whether its mission would be enhanced by the addition of concealed weapons."

The veto comes just four days after a horrific shooting in Newtown, Conn., in which a heavily armed 20-year-old muscled his way into the Sandy Hook Elementary School and killed 20 first-graders and six adults.

The Republican governor came under intense pressure in recent days from religious, medical and education groups to veto the concealed-carry bill and President Barack Obama called on the nation to take definitive action to ensure that no such tragedy happens again.

Senate Bill 59 was passed late Thursday by the Republican-controlled Legislature in the final hours of a frenetic lame duck session, in which all sorts of controversial legislation was passed and sent to Snyder.

The bill was intended to clarify that "open carry" of guns is not permitted on school properties, while allowing people with concealed pistol licenses and advanced training to carry concealed pistols in places where they normally couldn't, such as schools and public arenas.

But the law also was intended to include opt-out provisions for schools and other protected places that don't want any guns -- concealed or otherwise -- on their premises.

The bill said a private property owner may prohibit an individual from carrying a pistol, concealed or otherwise, on premises listed in Subsection 1. The list in that subsection includes, schools, along with bars, sports arenas and public or private day cares.

But public schools don't have private property owners, so public schools arguably would not have been able to use the wording in the legislation to prevent someone with a handgun carry permit and advanced training from carrying a weapon on school property.

On Monday, Snyder said the lack of a clear opt-out for schools and other public facilities was among his concerns, said spokeswoman Sara Wurfel.

"I was hoping he would veto it before last Friday," said state Sen. Gretchen Whitmer, a Democrat from East Lansing, Mich.

The bill didn't reach Snyder's desk until Tuesday afternoon.

As soon as word leaked out that Snyder planned to veto the bill, groups opposed to the legislation lauded the governor for his action.

"Gov. Snyder is making the right call by rejecting this dangerous legislation," said Zack Pohl, executive director of Progress Michigan. "This is a victory for school safety and common sense. We need more math and science teachers in our classrooms, not more guns. Snyder deserves credit for finally standing up to the extreme forces in his own party. Now it's time for Lansing politicians to get their priorities straight and start working together to create jobs and improve education."

Snyder did sign two other pro-gun bills Tuesday. One streamlines buying handguns, the other allows residents to buy rifles and shotguns from any state. Previously, Michiganders could buy rifles and shotguns only from contiguous states -- meaning Ohio, Indiana, Wisconsin and, because of their Lake Superior border, Minnesota.